Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.65: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

One- and two-particle excitations in the doped 2-dim. Hubbard model; a DCA calculation — •Stephan Hochkeppel, Fakher Assaad, and Werner Hanke — University of Wuerzburg, Wuerzburg, Germany

Using the Dynamical Cluster Approximation (DCA) and quantum Monte Carlo as a cluster solver we compute the single particle spectral functions of the electron and hole doped Hubbard model as a function of temperature. We allow U(1) as well as SU(2) symmmetry breaking baths so as to access superconducting states as well as antiferromagnetic order.
Two-particle quantities are computed within an extended RPA scheme where a dynamical vertex is extracted from the cluster and dressed Green function are used to calculate the bubble. The quality of the RPA approach is tested by comparing the resulting Neel temperature to that obtained by allowing for symmetry breaking within the DCA. Furthermore at high temperatures the collective spin excitations are compared with exact Monte Carlo simulations. Finally the temperature dependence of the single particle spectral function from the paramagnetic phase to superconducting state is studied in detail, the aim being a detailed study of the evolution of the pseudogap.